Gas turbine engines are used in myriad environments for myriad uses. For example, many aircraft include gas turbine engines to function as the main propulsion engines. The main propulsion engines, in many aircraft, not only provide propulsion for the aircraft, but may also be used to drive various other rotating components such as, for example, generators, compressors, and pumps, to thereby supply electrical and/or pneumatic power. However, when an aircraft is on the ground, its main engines may not be operating. Moreover, in some instances the main propulsion engines may not be capable of supplying the power needed for propulsion as well as the power to drive these other rotating components. Thus, many aircraft include one or more additional gas turbine engines to function as auxiliary power units (APUs). An APU, when operational, supplements the main propulsion engines in providing electrical and/or pneumatic power.
No matter its specific end-use environment or function, a gas turbine engine may include a rotatable drive shaft that is connected to a gear train housed in a gearbox for transferring force to and from the drive shaft. The gearbox can define various interfaces for various accessories to be mounted on the gearbox. These accessories may include, for example, a starter-generator, a fuel control component, and a lubrication pump.
As with numerous other rotating machines, the starter-generator needs to be supplied with lubrication. This can increase lubrication pump weight and complexity, since additional scavenge elements may need to be provided in order to scavenge lubricant from the starter-generator. This may also require additional filtration components to filter the scavenged lubricant, as well as additional gearbox coring to connect all of the relevant interfaces. All of these considerations can increase overall system weight, cost, and complexity.
Hence, there is a need for a means to reduce overall system weight, cost, and complexity, while providing adequate lubrication and scavenging functions for a gas turbine engine starter-generator. The present invention addresses at least this need.